Alternator failure -- twice!

Last year the alternator on my Toyota cooked the stator windings. I didn¹t
look any further and replaced it with a rebuilt alternator & regulator from
the local parts supplier.

Now (7 or 8 months later) the replacement has failed in the same mode. I¹m
suspicious. Also confused:

If a diode opens there wouldn¹t be an increased load on the stator windings.
If a diode shorts, there also wouldn¹t be any increase, just a decrease in DC
output voltage.

If the alternator output is shorted, since it¹s connected directly to the
battery (+) terminal, this would result in smoke and fire, at least a burnt
fusible link. None of this has occurred. (Well, the windings are discolored
and the smell is what clued me in to these problems.) When I put in a
replacement alternator I¹m quite confident everything will look just fine.
Until next time. *

What could cause these symptoms? Twice?

Thanks!

Sparky wrote:
> Last year the alternator on my Toyota cooked the stator windings. I didn¹t
> look any further and replaced it with a rebuilt alternator & regulator from
> the local parts supplier.
>
> Now (7 or 8 months later) the replacement has failed in the same mode. I¹m
> suspicious. Also confused:
>
> If a diode opens there wouldn¹t be an increased load on the stator windings.
> If a diode shorts, there also wouldn¹t be any increase, just a decrease in DC
> output voltage.
>
> If the alternator output is shorted, since it¹s connected directly to the
> battery (+) terminal, this would result in smoke and fire, at least a burnt
> fusible link. None of this has occurred. (Well, the windings are discolored
> and the smell is what clued me in to these problems.) When I put in a
> replacement alternator I¹m quite confident everything will look just fine.
> Until next time.
>
> What could cause these symptoms? Twice?
>
> Thanks!

Heat and poor quality alternators.
My old Pontiac used to burn up a $60 alternator every year for years
until I got tired of replacing them and got a $180 alternator.
That one lasted the remaining life of the car, about 6 more years.

On Monday, February 16, 2015 at 9:32:46 PM UTC-6, Paul in Houston TX wrote:
> Sparky wrote:
> > Last year the alternator on my Toyota cooked the stator windings. I didn¹t
> > look any further and replaced it with a rebuilt alternator & regulator from
> > the local parts supplier.
> >
> > Now (7 or 8 months later) the replacement has failed in the same mode. I¹m
> > suspicious. Also confused:
> >
> > If a diode opens there wouldn¹t be an increased load on the stator windings.
> > If a diode shorts, there also wouldn¹t be any increase, just a decrease in DC
> > output voltage.
> >
> > If the alternator output is shorted, since it¹s connected directly to the
> > battery (+) terminal, this would result in smoke and fire, at least a burnt
> > fusible link. None of this has occurred. (Well, the windings are discolored
> > and the smell is what clued me in to these problems.) When I put in a
> > replacement alternator I¹m quite confident everything will look just fine.
> > Until next time.
> >
> > What could cause these symptoms? Twice?
> >
> > Thanks!
>
> Heat and poor quality alternators.
> My old Pontiac used to burn up a $60 alternator every year for years
> until I got tired of replacing them and got a $180 alternator.
> That one lasted the remaining life of the car, about 6 more years.

There is an auto electric shop about a mile from me. Alternator, or starter motor, I always take them to that shop and let them rebuild them for me.

On Mon, 16 Feb 2015 19:22:14 -0800, Sparky > wrote:

>Last year the alternator on my Toyota cooked the stator windings. I didn¹t
>look any further and replaced it with a rebuilt alternator & regulator from
>the local parts supplier.
>
>Now (7 or 8 months later) the replacement has failed in the same mode. I¹m
>suspicious. Also confused:
>
>If a diode opens there wouldn¹t be an increased load on the stator windings.
>If a diode shorts, there also wouldn¹t be any increase, just a decrease in DC
>output voltage.
>
>If the alternator output is shorted, since it¹s connected directly to the
>battery (+) terminal, this would result in smoke and fire, at least a burnt
>fusible link. None of this has occurred. (Well, the windings are discolored
>and the smell is what clued me in to these problems.) When I put in a
>replacement alternator I¹m quite confident everything will look just fine.
>Until next time. *
>
>What could cause these symptoms? Twice?
>
>Thanks!
>

I've been told that things that cause problems include bad grounding
of the alternator and bad batteries.

> I've been told that things that cause problems include bad grounding
> of the alternator and bad batteries.

The battery was replaced at the same time as was the alternator: 5 months ago
(corrected from my original post).*

Measurement of battery cables: from battery cable (+) terminal to alternator
(+) terminal: 1.5 ohms. From battery cable (-) terminal to chassis: 1.5
ohms.*

Charging numbers with new alternator & 5 months old battery:
With partially (50%?) depleted battery, when the car was started and engine
revved, the new alternator output 34 amps, headlights off. With lights on
high, output was 44 amps. Charge voltage was 14.04 volts. These numbers are
within those specified in the Toyota factory manual (charge current: ³30A or
more²; charge voltage: ³13.9-15.1².*

Thanks.

Sparky > wrote:
>> I've been told that things that cause problems include bad grounding
>> of the alternator and bad batteries.
>
>The battery was replaced at the same time as was the alternator: 5 months ago
>(corrected from my original post).*

Take the thing to a small rebuilding shop, and ask them about the quality of
the winding material that was used.

There is a big difference between a rebuild using high temperature wire and
some crappy Autozone rebuild using undersized varnished wire.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Could be a bad batch of alternators. I manage an auto parts store and we just had an issue with a starter going up every couple of months. You could always try another brand.

On Monday, February 16, 2015 at 10:22:16 PM UTC-5, Sparky wrote:
> Last year the alternator on my Toyota cooked the stator windings. I didn¹t
> look any further and replaced it with a rebuilt alternator & regulator from
> the local parts supplier.
>
> Now (7 or 8 months later) the replacement has failed in the same mode. I¹m
> suspicious. Also confused:
>
> If a diode opens there wouldn¹t be an increased load on the stator windings.
> If a diode shorts, there also wouldn¹t be any increase, just a decrease in DC
> output voltage.
>
> If the alternator output is shorted, since it¹s connected directly to the
> battery (+) terminal, this would result in smoke and fire, at least a burnt
> fusible link. None of this has occurred. (Well, the windings are discolored
> and the smell is what clued me in to these problems.) When I put in a
> replacement alternator I¹m quite confident everything will look just fine.
> Until next time. *
>
> What could cause these symptoms? Twice?
>
> Thanks!

On Tue, 17 Feb 2015 12:08:33 -0800 (PST)
JR > wrote:

> There is an auto electric shop about a mile from me. Alternator, or
> starter motor, I always take them to that shop and let them rebuild
> them for me.

but if it's a junky alternator to start with aren't you still going
to have a junky rebuilt alternator

what do they do when they rebuild one?

Electric Comet > wrote:
>On Tue, 17 Feb 2015 12:08:33 -0800 (PST)
>JR > wrote:
>
>> There is an auto electric shop about a mile from me. Alternator, or
>> starter motor, I always take them to that shop and let them rebuild
>> them for me.
>
>but if it's a junky alternator to start with aren't you still going
>to have a junky rebuilt alternator

Possibly. If so, they'll probably tell you it's not worth rebuilding.

>what do they do when they rebuild one?

They take the whole thing apart and check all the individual parts. They
replace all wear items like brushes, bushings, and bearings. If a winding
is bad they'll replace it. They'll test the rectifiers and regulator
circuit and replace anything bad on it. They'll put it back together and
load test it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 20 Feb 2015 15:03:30 -0500
(Scott Dorsey) wrote:

> Possibly. If so, they'll probably tell you it's not worth rebuilding.

this is good

> They take the whole thing apart and check all the individual parts.
> They replace all wear items like brushes, bushings, and bearings. If
> a winding is bad they'll replace it. They'll test the rectifiers and
> regulator circuit and replace anything bad on it. They'll put it
> back together and load test it.

seems to be that these kinds of shops are fewer and farther between
the nature of the throw-away manuf/engineering designs of most things
now